In essence, Tower Defense Games are real-time strategies with immobile units. As in a complex chessboard where the pieces are cast in stone to never move again. However, anyone who dares cross the areas of their control will be incinerated. Pure and simple.

But we are not talking about chess. Initially, this sub-genre of strategy games equips the player with certain amount of resources which are to be used for the erection of defenses. Most of the games allow the player to build towers along the way and use them as weapons for mass destruction against the enemy. If the defenses fail, the player loses hit points of some sort. In many cases, the only way to acquire new resources for upgrades and new towers is through killing enemies. Any attacker who reaches the other side inflicts wound twofold: by chopping off hitpoints and by stalling further progress. A dangerous spiral which has led many a Tower Defense Games player to swift and brutal demise. Of course, by far not all games of the sub-genre are bloody or violent. Take Keeper Of The Grove, for instance. It is a cute little game, full of flowers and diamonds. Your diamonds. And sneaky little critters who want to take them. Your flowers can gun them down easily. Is there a choice here, really? Naturally, there is lot of killing going on in a good number of Tower Defense Games; the name suggests as much. Sometimes the killing is depicted in greater detail, but often it appears through imaginative art forms.

If taken literally, the title of the genre could mean the defense of a single tower. Master of Fortresses is a bright example of the latter. In it, the player must protect a fort from being overtaken by the invaders. He or she can put traps and obstacles on their path, creating zones of death for the enemy troops. After each wave, whatever is left from the fort can be upgraded and repaired for the next attack. On the other hand, we have games like Steampunk Tower Defense. There the player literally defends one single tower. His strategy is based on a number of cannons with different strengths. So far so good, but these cannons can be moved from one side of the tower to the other. Secondly, there is no map; the enemies simply come from each side of the screen to be brutally slaughtered. This makes it resemble much closer a defense game and not a tower defense.

Towers with various utilities and maps are the tactical and strategic side of the coin called Tower Defense Games. In some of them the route which the enemies follow is predefined. The defined enemy path requires more tactical control over the area. But in Master of Fortresses or Whiteboard Tower Defense the player must devise ways to guide the enemies in their early graves. Traps and obstacles diversify the gameplay a lot, adding even more appeal to this type of games, calling for greater grasp of strategy.